The invention relates generally to chain saws and more particularly to an improved cutter bar and cutter bar safety guard which protects against accidental contact with the saw chain carried on the longitudinal side edges of a cutter bar.
Chain saws are inherently dangerous implements for both experienced and inexperienced operators. Even the briefest accidental contact between the saw operator and a moving saw chain can cause serious and often permanent injury. Because of the potential for dangerous accidents, numerous devices have been developed and patented over the years to protect the chain saw operator. Examples of prior art safety guards include devices which extend along one edge of the cutter bar and pivot out of the way, as shown in U.S. Pat. Nos. 3,384,136 and 4,060,894; pivoting covers which fully or partially sheath the cutter bar and pivot out of the way during use, as shown in U.S. Pat. Nos. 3,059,673 and 4,257,162; or a telescoping full saw enclosure which collapses out of the way of the cutter bar, as shown in U.S. Pat. No. 2,638,944. Many of these prior art devices are cumbersome to use, can become clogged with sawdust and wood chips, and may seriously interfere with the operator's view of the cutter bar when the saw is in use. For these and other reasons, most chain saw safety guard devices remain unpopular with saw owners and manufacturers.
It would be advantageous to have a chain saw safety guard device which did not obstruct the operator's view of the cutter bar or the object being cut.
It would also be advantageous to have a chain saw safety guard which only minimally interfere with cutting operations.
It would also be advantageous to have an improved cutter bar for chain saws which avoided overheating and was compatible with the safety guard of the present invention.
Accordingly, the present invention provides a chain saw safety guard for protecting against accidental contact with the longitudinal side edges of a chain saw cutter bar. The safety guard comprises a generally U-shaped guard member which includes a pair of guard rails extending generally parallel with one another to the open end of the U, and a cross-piece extending between the rails at the closed end of the U. Rail supports are provided on the chain saw for supporting the rails of the guard member such that the rails are longitudinally adjacent and spaced from the side edges of the cutter bar. The rail supports permit longitudinal movement of the rails along the side edges of the cutter bar. And a forward support is provided which includes a longitudinal track o the cutter bar and a track-engaging traveler operatively connected to the cross-piece of the guard member. The guard member is supported relative to the cutter bar at three points, the two rail supports and the forward support. It is movable longitudinally along the cutter bar to expose the side edges thereof when the chain saw is used to cut objects.
The preferred form of the safety guard includes a longitudinal slot in the cutter bar, extending generally along portions of the central longitudinal axis of the cutter bar. The slot is part of the longitudinal track on the forward support of the cutter bar. The safety guard preferably extends only part of the way to the tip or distal end of the cutter bar. In other words, when the guard is fully extended, the side rails and cross-piece are spaced a predetermined distance back from the tip of the cutter bar. That allows the chain saw operator to engage an object being cut using the traveling saw chain on the "unguarded" tip of the cutter bar. As the user begins to cut into the object, the object engages and pushes against the outer end of the safety guard, causing it to retract along the cutter bar, which exposes the side edge of the cutter bar so the object can be cut.
The invention also provides an improved chain saw cutter bar of the type which is attached to a chain saw motor housing at its proximal end and which includes an elongated inflexible plate member extending outwardly therefrom. The cutter bar has a width and length substantially exceeding the thickness of the plate member. It also has a guide groove extending along portions of its periphery for guiding a saw chain along the longitudinal side edges of the cutter bar, and around the tip of the cutter bar. The improvement of the present invention comprises one or more openings which extend through the plate member to cool the cutter bar. The openings preferably include a longitudinally-extending elongated slot which cools the bar and which also serves as a track on the cutter bar for the forward support of the safety guard.